1. Field of the Invention
The present invention relates to a colored curable composition favorable for forming a color filter for use in liquid crystal display elements (LCD) and solid-state image pickup elements (for example, CCD and CMOS), a color filter using the colored curable composition, and a method for manufacturing the color filter.
2. Description of the Related Art
Examples of known color filters formed on an element for enabling a solid-state image pickup element or liquid crystal display element to display colors include, for example, color filters comprising a yellow filter layer, a magenta filter layer, and a cyan filter layer formed in adjoining relation to each other on a same plane on a substrate, and color filters comprising a red filter layer, a green filter layer, and a blue filter layer also formed in adjoining relation to each other on a same plane on a substrate. The filter layers comprise striped or mosaic patterns. Various methods for forming color filters have been proposed, with a color resist method having been widely used wherein a step for patterning a pigment-containing photosensitive resin composition by exposure and development is repeated a number of times required.
In the color resist method (hereinafter referred to as pigment dispersion method), pigment is dispersed in a variety of photosensitive compositions to prepare a colored radiation-sensitive composition, after which a color filter is manufactured through photolithography using the composition. This method is suitable for manufacturing a color filter for a large screen, precise-color display, since the color filter is stable with respect to light, heat and other influence due to the use of the pigment, and positional accuracy is sufficient as a result of patterning by photolithography.
The method for manufacturing a color filter with the above pigment dispersion method comprises the steps of applying the radiation sensitive composition on a glass substrate using a spin coater or roll coater to form a coating film, obtaining colored pixels by pattern exposure and development of the coating film, and repeating this procedure for every colors to obtain a color filter. Regarding the pigment dispersion method, a negative photosensitive composition has been disclosed which is prepared by using an alkali-soluble resin, a photopolymerizable monomer, and a photopolymerization initiator (see, for example, Japanese Patent Application Laid-Open (JP-A) Nos. 1-102469, 1-152499, 2-181704, 2-199403, 4-76062, 5-273411, 6-184482 and 7-140654).
Color filters for solid-state image pickup elements have been required to be finer and more precise in recent years. However, since conventional pigment dispersion methods involve the problem of poor image resolution and irregular coloring due to coarse pigment particles, such methods are not suitable for uses requiring a fine pattern as in a solid-state image pickup element. Use of a dye has been proposed for solving these problems, and positive-type photosensitive compositions have been disclosed (for example, see JP-A Nos. 6-75375 and 2002-14221, and Japanese Patent Application Publication (JP-B) No. 7-111485).
However, the dye-containing colored curable compositions also involve the following problems and a need for further improvement is required.
(1) Since dye is usually poor in such characteristics as heat resistance and light fastness compared to pigment, more improvement in durability is required.
(2) A large quantity of dye needs to be added when the dye has a low molar absorbance coefficient. This forces the proportion of other components such as a polymerizable compound, binder, and photopolymerization initiator in the colored curable composition to be reduced. The result is that curability, heat resistance after curing, and developability of non-cured portions is deteriorated, and therefore improvement is needed.
(3) The dye often interacts with other components in the colored curable composition, making it difficult to control cured portions and developablity (solubility) of cured portions, again requiring improvement.
In particular, durability has not been satisfactory in dyes used in the conventional photosensitive compositions as described above, and further, it was difficult to add the dye to the photosensitive composition in high concentration due to low solubility of the dye in the composition. Improvement had been desired for these properties.
A violet pigment has been used in a blue filter of the color filter (for example, see JP-A No. 2002-14222). However, heat resistance and light fastness of the violet pigment used in that patent is insufficient and improvements in these properties are required. Similarly, improvement in durability of the magenta pigment used in the magenta filter layer of the color filter comprising the yellow filter layer, magenta filter layer, and cyan filter layer has been also desired. Color filters containing a pyrazoroazole-base azomethin pigment have been disclosed (see, for example, JP-A No. 2002-256164), however, these dyes also require improvement in solubility and durability.